ForSyDe.Shallow.Signal

This module defines the shallow-embedded Signal datatype and functions operating on it.

Documentation

data Signal a

A signal is defined as a list of events. An event has a tag and a value. The tag of an event is defined by the position in the list. A signal is defined as an instance of the classes Read and Show. The signal 1 :- 2 :- NullS is represented as {1,2}.

Constructors

NullS

a :- (Signal a)

Instances

Eq a => Eq (Signal a)

Read a => Read (Signal a)

Show a => Show (Signal a)

(-:) :: Signal a -> a -> Signal a

The operator -: adds at an element to a signal at the tail.

(+-+) :: Signal a -> Signal a -> Signal a

The operator +-+ concatinates two signals into one signal.

(!-) :: Signal a -> Int -> a

signal :: [a] -> Signal a

The function signal converts a list into a signal.

fromSignal :: Signal a -> [a]

The function fromSignal converts a signal into a list.

unitS :: a -> Signal a

The function unitS creates a signal with one value.

nullS :: Signal a -> Bool

The function nullS checks if a signal is empty.

headS :: Signal a -> a

The function headS gives the first value - the head - of a signal.

tailS :: Signal a -> Signal a

The function tailS gives the rest of the signal - the tail.

atS :: Int -> Signal a -> a

The function atS returns the n-th event in a signal. The numbering of events in a signal starts with 0. There is also an operator version of this function, '(!-)'.

takeS :: Int -> Signal a -> Signal a

The function takeS returns the first n values of a signal.

dropS :: Int -> Signal a -> Signal a

The function dropS drops the first $n$ values from a signal.

lengthS :: Signal b -> Int

The function lengthS returns the length of a finite signal.

infiniteS :: (a -> a) -> a -> Signal a

The function infiniteS creates an infinite signal. The first argument f is a function that is applied on the current value. The second argument x gives the first value of the signal.

 Signal> takeS 5 (infiniteS (*3) 1)
 {1,3,9,27,81} :: Signal Integer

copyS :: Num a => a -> b -> Signal b

The function copyS creates a signal with n values x.

selectS :: Int -> Int -> Signal a -> Signal a

The function selectS takes three parameters, an offset, a stepsize and a signal and returns some elements of the signal such as in the following example:

 Signal> selectS 2 3 (signal[1,2,3,4,5,6,7,8,9,10])
 {3,6,9} :: Signal Integer

writeS :: Show a => Signal a -> [Char]

The function writeS transforms a signal into a string of the following format:

 
 Signal> writeS (signal[1,2,3,4,5])
 1n2n3n4n5n :: [Char]

readS :: Read a => [Char] -> Signal a

The function readS transforms a formatted string into a signal.

 Signal> readS 1n2n3n4n5n :: Signal Int
 {1,2,3,4,5} :: Signal Int

fanS :: (Signal a -> Signal b) -> (Signal a -> Signal c) -> Signal a -> (Signal b, Signal c)

The combinator fanS takes two processes p1 and p2 and and generates a process network, where a signal is split and processed by the processes p1 and p2.